1. Field of the Invention
The present invention relates to speed reducers adapted to ensure angular actuation of the movable members of robots, industrial manipulators, rotary machining plates and other like applications.
2. History of the Related Art
It is known that, in this type of apparatus, there is provided for each movable member a kinematic chain comprising an input shaft driven by an autonomous motor and connected, via a speed reducer, to an output shaft secured to the movable member. As the speed of rotation of the input shaft is much higher than that desired for the output shaft, reducers of the cycloidal type are ordinarily employed.
It will be recalled that a conventional cycloidal reducer comprises in principle at least one eccentric (in fact, two opposite eccentrics are most often employed in order to obtain a better balancing of forces), which is connected to the input shaft with to ensure, by rotation, the control of a circular cam whose periphery is toothed in order to cooperate with fixed teeth. The number of fixed teeth is slightly greater (in practice by one unit) than that of the periphery of the cam. In addition, there is associated with the cam at least one actuation finger which is carried by a plate angularly connected to the output shaft and which is engaged inside a housing made in the cam (or, in the ordinary case of two parallel cams, in a housing defined by two conjugate openings of the two cams).
It will be understood that the primary motion applied by the input shaft to the eccentric causes the corresponding toothed cam to roll on the fixed outer teeth and thus to ensure, via the actuation fingers, drive of the output shaft in a ratio which depends on the number of teeth of the cam and on the difference of this number with respect to that of the fixed toothing, the cam backing by this difference for a revolution of the eccentric.
It will be readily appreciated that, for the correct functioning of such a cycloidal reduction system to be satisfactory, it is indispensable that all the parts of the mechanism be subjected to very precise machining completed by a careful finish or a pairing of the elements at assembly, which obviously increases, very substantially, the cost price of the speed reducer assembly.